Corrosion inhibiting lubricating oil



United States Patent CORROSION INHIBITING LUBRICATING 01L Charles H- Whitacre, Cleveland, Ohio, assignor to The Standard Oil Company, Cleveland, Ohio, a corporation of Ohio NoDrawing: Application March 16, 1956 Serial No. 571,876

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The present invention relates to improved lubricating oils. More particularly, the inventionrelates to a corrosion inhibiting oil adapted to-be used in the lubrication of an internal combustion engine.

One of the causes of wear. in an internal' combustion engine is corrosion of the metal. surfaces of such an engine. Such corrosion results from the action of various corrosion-promoting compounds which tend toaccumulate in the crank case of the engine. The corrosionpromoting compounds present in the crankcase are principally water and various'weak. organic acids which may result from engine blow-by" or from degradation of the lubricating oil. Regardless of the source of the corrosion-promoting. compounds, it is important. to protect the engine from the deleterious action of such compounds andthereby reduce engine wear.

- The problem of corrosion ininternal combustion engines is accentuated to some extent in engines employing so-called premium grade automotive lubricating oils. Premium grade automotive lubricants are characterized by a high viscosity index" and they usually contain a combination of detergent and. dispersant additives as well as the usual viscosity index improvers, pour point depressants, and oxidation inhibitors. Such additives will both remove and-prevent the accumulation of deposits on the various metal surfaces of the engine which come into contact. with the lubricating oil during the operation of the engine. Since the aforesaid deposits, although undesirableifor other reasons, would otherwise provide a measure of corrosion protection forthe metal surfaces on which they adhere, the removal of the deposits renders the surfaces thus exposed more susceptible to corrosive attack. Hence, it is important that the socalled premium grade lubricants possess the property of inhibiting corrosion of metal surfaces.

Accordingly, it is the object of this invention to prepare an improved lubricating oil which inherently possesses a corrosion inhibiting effect.

In brief, my invention is an improved lubricating oil consisting essentially of a hydrocarbon oil of lubricating viscosity, an oil-soluble alkaline earth metal sulfonate and a polyoxyethylated alkylphenol. The sulfonate may be present in amounts ranging from about 0.15 to about 1.0 weight percent, while the amount of polyoxyethylated alkylphenol in the composition should range from about 0.1 to about 1.0 weight percent.

As the oil base of this invention, any hydrocarbon oil of lubricating viscosity may be employed. Synthetic lubricating oils, as well as petroleum derived oils, may be conveniently employed. The oil may be refined or not. However, it is preferred to use a refined hydrocarbon oil derived from a crude petroleum which may be refined by any of the conventional methods such as by solvent extraction or by treatment with sulfuric acid.

The alkaline earth metal sulfonate of this invention Patented May 6, 1958 ice which may be used in connection withthis inventionare' oil-soluble mahogany sulfonicacids and oil-soluble petrolatum sulfonic acids. The oil solubility of the sulfonates is determined by their' molecular weight and, generally, only the higher molecular weight sulfonates are oil-soluble. The preferred alkaline earth metal sulfonate is barium petroleum sulfonate, preferably having a molecular weight in the range of about 950 to 1050. A stabilizer may be employed in conjunction with the alkaline earth metal sulfonate such as, for example, barium phenate, but such stabilizers are not required in order to achieve the results of thisinvention.

The polyoxyethylated alkylphenol of' this invention may be any oil-soluble member of the group of con'lpounds having the general formula listed below:

where R may be either a straight or branched chain'ajllqyl group containing between about 8 to 20 carbon atoms.

Generally speaking, compounds of this type in which n is greater than about 4 will not be oil-soluble and compounds in which n is less than 2 will be unsuitable for other reasons. This type of compound is prepared by the polymerization of ethylene oxide with a phenolic base-in the presence of a strong base as is explainediii U. S. Patent No. 2,213,477. The reaction is a random one and'a single compound is not obtained, but a mixture of closely related materials in which n varies from'th e mean value.

tained in the compounds are averages. The preferred compound for the purposes of this invention is-a polyoxyethylated isononylphenol which has the following structural formula:

cosity of 140SUS at' F. and a solvent extracted neutral oil having a viscosity of 300 SUS at 100 F. Both of the aforesaid oils were derived from a midcontinent crude oil. The additives incorporated in these oils were an oil-soluble barium petroleum sulfonate having an average molecular weight of about 980 and a polyoxyethylated nonylphenol having the formula set forth above for the preferred compound.

The prepared oils were tested in a modification of ASTM test D-665 which is a turbine oil anti-rust test. This test is carried out in the following manner: A 300 ml. sample of the oil to be tested is placed in a beaker equipped with an automatic stirrer. The beaker is then placed in an oil bath-which is maintained at a temperature of F. When the oil sample has reached a temperature of approximately 140 F., a specimen which is a strip of low carbon steel having a clean surface is suspended above the oil sample so as to be partially immersed therein. After a 15-minute period during which the oil is stirred, 30 ml. of a 1% aqueous solution of glacial acetic acid are added to and mixed in with the oil sample. The specimen is removed and visually examined for signs of corrosion at intervals of one hour during the first 6 hours of the test and at the completion of the first 24 hours of the test and at 24 hour intervals thereafter until a total time of 500 hours has elapsed. If the specimen shows no sign of corrosion at the end of 500 hours, the oil is given a rating of 500+ and this is the Accordingly, all figures presented herein regarding the number of mols of ethylene oxide conhighest rating. If the specimen shows no sign of corrosion at the end of 200 hours, the oil tested is rated as satisfactory. The data obtained in the test for the various oils which I have compounded are reported in Table I.

TABLE I Amounts. in weight percent Asindicated in Table I, the oils of Examples 5, 6, 9, 10, 13 and 14 were satisfactory or better and all of the other oils failed the test. It was concluded from the data reported in Table I that the improved corrosion inhibiting properties are imparted to an oil only if it contains at least about 0.15 weight percent of the oil-soluble alkaline earth metal petroleum sulfonate and at least about 0.10 weight percent of the polyoxyethylated alkylphenol. There is generally no upper limit to the effective concentration of these additives, but there are economic factors involved and it is generally uneconomic to include more than 1% by weight of either additive.

From the above data I conclude that the best mode contemplated for carrying out my invention is a lubricating oil in which a solvent extracted neutral stock of lubricating viscosity is employed as the oil base and containing 0.5% of an oil-soluble barium petroleum sulfonate having a molecular weight of about 980 and 0.1% 'of polyoxyethylated isononylphenol having the following structural formula:

straw-Que 011mm:

The improved corrosion inhibiting properties of the oils prepared in accordance with my invention are not affected by any of the usual lubricating oil additives or color dyes and, accordingly, such additives may be added to the oils of my invention without interference to the beneficial corrosion inhibiting properties. For example, an oil might contain, in addition to the corrosion inhibiting additives described above, a detergent or dispersant additive such as one of the copolymers of lauryl methacrylate and diethylamino ethyl methacrylate. The oil might also contain any of the conventional viscosity index improvers or pour point depressants such as, for example, the esters of methacrylic acid and higher fatty alcohols such as cetyl or lauryl, the condensation product of parafiin wax and naphthalene, orany of the butene polymers having molecular weights in the order of 10,000 to 15,000. Additionally, the oil might contain any of the conventional oxidation inhibitors such as, for example, zinc dithiophosphate. Moreover, any combination of such additives may be employed with the oils of my invention without detrimental results. Accordingly, the term consisting essentially of, as used in the appended claims, is not meant to exclude materials which will not materially alter the beneficial properties of my compositions.

I claim: 1

1. A lubricating composition consisting essentially of an oil base of lubricating viscosity, at least about 0.15

weight percent of an oil-soluble barium petroleum sulfonate, and at least about 0.1 weight percent of a polyoxyethylated alkylphenol having the following structural formula:

R-O(GHz-CHr-0,0H

formula:

otnn--o(oolm ton References Cited in the file of this patent UNITED STATES PATENTS 2,681,315 Tongberg et al. June 15, 1954 UNITED STATES PATENT OFFICE Certificate of Correction Patent No. 2,833,717 May 6, 1958 Charles H. Whitacre It is hereb certified that error appears in the printed specification of l the above num ered patent requiring correction and that the said Letters Patent should read as corrected below.

Column 4, lines 33 to 35 inclusive, the formula should appear as shown below instead of as in the patent:

Signed and sealed this 10th day of June 1958.

Attest: KARL H. AXLINE, ROBERT C. WATSON,

Attesti/ng Oyficer. Oomzissz'oner of Patents. 

1. A LUBRICATING COMPOSITION CONSISTING ESSENTIALLY OF AN OIL BASE OF LUBRICATING VISCOSITY, AT LEAST ABOUT 0.15 WEIGHT PERCENT OF AN OIL-SOLUBLE BARIUM PETROLEUM SULFONATE, AND AT LEAST ABOUT 0.1 WEIGHT PERCENT OF A POLYOXYETHYLATED ALKYLPHENOL HAVING THE FOLLOWING STRUCTURAL FORMULA: 